1. Field of the Invention
The present invention relates to a switch used for turning a stop lamp on/off for example when a brake pedal of a motor vehicle is operated in particular, and a switch device using the switch.
2. Background Art
Recently, a pressure type switch is used as a switch for transmitting the operation of a brake pedal to a controller. When the operation of the brake pedal depressed is transmitted, the controller serves to turn on a stop lamp. With the brake pedal released, the controller serves to turn off the stop lamp.
Such a conventional switch is described with reference to FIG. 7 and FIG. 8. FIG. 7 is a sectional view of conventional switch 11. In the figure, casing 12 includes case 1 and cover 10. Case 1 is made of insulating resin and opens upward in the figure. Cover 10 is made of insulating resin and disposed so as to cover the opening of case 1. Cylinder 10A is disposed at the upper part of cover 10. Actuator 2 and spring 9 are disposed in casing 12. Actuator 2 is installed in such manner as to be vertically movable in cylinder 1A. In the figure, coil spring 9 is disposed between a hollow portion of actuator 2 and bottom 1A of case 1. Due to restoring force of resilient spring 9, actuator 2 is pressed against cover 10. End 2A of actuator 2 is protruded upward from cylinder 10A.
Casing 12 is internally provided with magnet 3 and detector 6 in such manner as to be opposed to each other. Magnet 3 is disposed on the lower side surface of actuator 2. Detector 6 is formed of Hall Element and the like and disposed on wiring board 5. On wiring board 5 are disposed switching part 7 such as transistor or the like, and controller 8 formed of FET and a plurality of fixed resistors, etc. As to a plurality of terminals 4 made of conductive metal, one end thereof is connected to wiring board 5, and the other end is protruded outside the casing 12 from hole 1B of bottom 1A. Wiring patterns are provided on the right and left surfaces of wiring board 5. Terminal 4, detector 6, switching part 7, and controller 8 are electrically connected via the wiring patterns. These electronic parts are electrically connected by using solder or the like.
FIG. 8 shows a state of above-mentioned switch 11 mounted in a motor vehicle. Switch 11 and arm 30A are fitted to holding member 36. Arm 30A and holding member 36 are connected to each other on fulcrum 30B of arm 30A. Brake pedal 30 is attached to the tip of arm 30A. Arm 30A and switch 11 are in contact with each other via the end 2A of actuator 2. Connector 31 is connected to switch 11. Terminal 4 shown in FIG. 7 connects to a stop lamp and ignition switch of the motor vehicle, battery, electronic circuits of the motor vehicle, etc. via lead wires 31A of connector 31.
In FIG. 8, the state of arm 30A and brake pedal 30 shown by solid line indicates a state obtained when brake pedal 30 is not depressed. The state of arm 30A and brake pedal 30 shown by broken line indicates a state obtained when brake pedal 30 is depressed.
In this case, switch 11 shown in FIG. 7 changes as described in the following when brake pedal 30 is depressed. When brake pedal 30 is not depressed, the pressing force is applied downward in FIG. 7 to the end 2A of actuator 2. In other words, actuator 2 is in a state of being pressed downward. Magnet 3 disposed on the side surface of actuator 2 moves downward along with actuator 2. When brake pedal 30 is pressed, magnet 3 confronted detector 6, and when brake pedal 30 is not depressed, magnet 3 is positioned far away from detector 6. Consequently, the magnetism of magnet 3 detected by detector 6 becomes very weak.
Controller 8 operates as follows in accordance with the intensity of magnetism detected by detector 6.
When the magnetism detected exceeds the specified value, controller 8 detects that switch 11 is ON. As a result, controller 8 sets switching part 7 to ON and turns on the stop lamp. When the magnetism detected is less than the specified value, controller 8 detects that switch 11 is OFF. As a result, controller 8 sets the switching part 7 to OFF and turns off the stop lamp.
As described above, with actuator 2 depressed downward, the magnetism detected by detector 6 is very weak, that is, the magnetism is less than the specified value. Accordingly, controller 8 detects that switch 11 is OFF, then it sets the switching part 7 to OFF and turns off the stop lamp.
When brake pedal 30 is depressed, the inside of switch 11 shown in FIG. 7 becomes as described in the following. When brake pedal 30 is depressed, arm 30A moves apart from the end 2A of actuator 2. As a result, the pressing force applied to actuator 2 by means of arm 30A is released, and then, due to the restoring force of resilient spring 9, actuator 2 is moved upward. The condition is shown in FIG. 7. At the time, magnet 3 disposed on the side surface of actuator 2 moves upward along with actuator 2. As a result, magnet 3 and detector 6 become opposed to each other, intensifying the magnetism of magnet 3 detected by detector 6. In other words, the magnetism detected by detector 6 becomes higher than the specified value, and controller 8 detects that switch 11 is ON. And controller 8 sets switching part 7 to ON and turns on the stop lamp.
That is, conventional switch 11 operates as follows. Actuator 2 vertically moves in cylinder 10A in accordance with the operation of brake pedal 30. Magnet 3 disposed on the side surface of actuator 2 moves along with actuator 2. The magnetism detected by detector 6 varies in accordance with the movement of magnet 3. When the magnetism detected by detector 6 is higher than the specified value, controller 8 detects that switch 11 is ON. When the magnetism detected by detector 6 is less than the specified value, controller 8 detects that switch 11 is OFF. In accordance with the detection result of controller 8, controller 8 sets the switching part 7 to ON/OFF, and turns on/off the stop lamp.
As prior art, for example, Unexamined Japanese Patent Publication No. 2006-92777 is known.
Incidentally, in case of trouble with detector 6, the value transmitted from detector 6 to controller 8 becomes constant. Consequently, even when actuator 2 moves upward or downward, only a signal showing that switch 11 is OFF is transmitted from detector 6 to controller 8. That is, in the case of conventional switch 11, actuator 2 is pressed, and therefore, it is unable to detect whether OF is detected by detector 6 or OFF is detected because of trouble with detector 6.